Methods and Apparatus for Operating Wireless Devices

ABSTRACT

A system of operating a wireless device in a wireless communication network includes selecting, by the wireless device, a preferred operating mode for use by the wireless device, the selection being made from at least a full duplex operating mode in which the wireless device can transmit and receive simultaneously on the same frequency band and a non full duplex operating mode; and transmitting a signal indicating the selected preferred operating mode to a network entity.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit under 35 U.S.C. §119(a) and 37 CFR§1.55 to UK Patent Application No. 1203143.1 filed on Feb. 23, 2012, theentire content of which is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to methods and apparatus for operatingwireless devices in a wireless communication system.

BACKGROUND

Current wireless communication systems are typically eitherFrequency-Division Duplex (FDD) systems or Time-Division Duplex (TDD)systems. In FDD operation there are two carrier frequencies, one foruplink transmissions (user terminal to base station) and one fordownlink transmissions (base station to user terminal). Hence, in FDDsystems, uplink and downlink transmissions occur simultaneously but indifferent frequency bands. In TDD operation there is a single carrierfrequency only and the uplink and downlink transmissions are separatedin the time domain (e.g. occur in different system time slots). Hence,in TDD systems, uplink and downlink transmissions occur in the samefrequency band but not simultaneously.

The respective standards that define cellular wideband code divisionmultiple access (WCDMA) systems (so called 3G systems) and cellular longterm evolution (LTE) systems (so called 4G systems) specify systemvariants based on both FDD and TDD. Wireless local area networks (WLAN),for example WiMAX, tend to be TDD systems only.

Herein, communication systems in which it is not possible to transmitand receive simultaneously in the same frequency band will be referredto as half-duplex or non full-duplex systems. In contrast, communicationsystems in which it is possible to transmit and receive simultaneouslyin the same frequency band (e.g. with no frequency duplex spacingbetween the transmission and reception bands) will be referred to asfull-duplex systems. A frequency band refers to a frequency allocationassigned to a baseband signal after being up-converted on a certaincarrier frequency.

Full-duplex communication has been recognized as a candidate techniquefor improving spectral efficiency in local area communications, infull-duplex communication systems techniques must be applied to reducestrong ‘self-interference’ that would otherwise occur as a result of thelarge power imbalance between the simultaneously transmitted signal andreceived signal. Typically, the transmitted signal can have a signalstrength that is a few orders of magnitude larger than that of theintended received signal strength with the result that the intendedreceived signal can be severely degraded by the transmitted signal.

Known techniques for reducing self interference at a full duplextransceiver can be broadly categorised as techniques that rely on thelinear processing of antenna arrays at the transceiver to create atransmission null at the transceiver's receiver (referred to herein aslinear space domain interference processing techniques) as discussed forexample in references [1] or techniques that don't rely on the linearprocessing of antenna arrays at the transceiver but various othertechniques (referred to herein as non-linear interference processing)such as those disclosed in references [2] to [6] listed below:

-   [1] Riihonen, T.; Werner, S.: Wichbman, R.; “Mitigation of Loopback    Self-Interference in Full-Duplex MIMO Relays.” Signal Processing,    IEEE Transactions on wireless communications, vol. 59, no. 12, pp.    5983-5993. December 2011.-   [2] Jung Il Choiy, Mayank Jainy, Kannan Srinivasany, Philip Levis,    Sachin Katti, “Achieving Single Channel, Full Duplex Wireless    Communication”, In the Proceedings of the 16th Annual International    Conference on Mobile Computing and Networking (Mobicom 2010).-   [3] Melissa Duarte and Ashutosh Sabharwal, “Full-Duplex Wireless    Communications Using Off-The-Shelf Radios: Feasibility and First    Results”, in the proceedings of the 44^(th) annual Asilomar    conference on signals, systems, and computers 2010.-   [4] Melissa Duarte, Chris Dick and Ashutosh Sabharwal,    “Experiment-driven Characterization of Full-Duplex Wireless    Systems”. Submitted to IEEE Transactions on Wireless Communications,    July 2011.-   [5] Evan Everett, Melissa Duarte, Chris Dick, and Ashutosh    Sabharwal, “Empowering Full-Duplex Wireless Communication by    Exploiting Directional Diversity” accepted to the 45^(th) annual    Asilomar conference on signals, systems, and computers 2010.-   [6] Achaleshwar Sahai, Gaurav Patel and Ashutosh Sabharwal, “Pushing    the limits of Full-duplex: Design and Real-time Implementation”,    Rice university technical report TREE1104.

LTE and WiMAX communication systems, amongst others, employ MultipleInput Multiple Output (MIMO) techniques to enhance data rates(throughput) and spectral efficiency. As is well known, MIMO refers tothe use of multiple antennas at the receiver and multiple antennas atthe transmitter. Different modes of MIMO are known, including spatialmultiplexing, transmit diversity, and beam forming.

Spatial multiplexing allows the transmission of different independentlayers or streams of data simultaneously on the same downlink (or, asthe case may be, uplink) resources to increase data rates for a givenchannel bandwidth. Transmit diversity schemes increase the resilience ofa propagation channel, rather than increasing data rates, and are oftenused when channel conditions do not permit spatial multiplexing. Beamforming techniques provide for the shaping of the overall antenna beamin the direction of the target receiver and again are often used whenchannel conditions do not permit spatial multiplexing.

In a MIMO system, each receive antenna may receive the signaltransmitted from each transmit antenna and the channel between thetransmitter and the receiver can be described by a channel matrix Hincluding the matrix elements h_(ij), where h_(ij) is the channel gainfrom transmit antenna j to receive antenna i. If spatial multiplexing isemployed, the number of independent data layers or streams that canusefully be transmitted in parallel over a MIMO channel is at most theminimum of the number of receive antennas and the number of transmitantennas, and is further limited by the rank (i.e. the minimum number oflinearly independent rows and columns) of the channel matrix H. Incertain known communications systems, for example, LTE systems, spatialmultiplexing relies upon a user device (i.e. a mobile user equipment)providing periodic feedback to the base station (i.e. Node B) servingit. The feedback includes a so called Rank Indication (RI) determined bythe user device, based on channel and interference conditions, whichindicates a suggested number of layers for transmission on the downlinkto the user device. The base station may or may not follow thesuggestion provided by the user device.

In environments where the transmission antennas are not sufficientlyde-correlated, for example in a low scattering environment (i.e. wherethere are few or no objects to reflect signals from the differentantennas to the different receive antennas along different paths), therank of the channel matrix H is low and the potential throughputadvantages of spatial multiplexing cannot be utilized effectively.Typically, an environment is not sufficiently scattering enough towarrant the use of spatial multiplexing if a Line of Sight (LOS) existsbetween the transmitter and the receiver in a MIMO system which canresult in the rank of the channel matrix reducing to 1. In known systemsit is possible to switch between MIMO modes in response to changingchannel conditions, and typically, for rank 1 channels, transmitdiversity or beam forming is used instead of spatial multiplexing. It iswell-known that for rank one channels the maximum throughput of a halfduplex system is limited by the performance of the rank one transmitdiversity or beam forming pre-coding performed at the transmitter, powerallocation to the channel and the modulation and coding scheme (MCS)selected for the channel.

Wireless systems have been proposed in which it is possible toselectively use a full duplex operation mode instead of a half duplexmode, under certain channel conditions, in order to improve throughput.It is desirable to provide a system in which the signalling schemes usedto configure devices in a full duplex operation mode or a half duplexoperating mode and/or schedule the devices are straightforward.

SUMMARY

In a first exemplary embodiment of the invention, there is an apparatusfor a wireless device operating in a wireless communication network, theapparatus including: at least one processor; and at least one memoryincluding computer program code, the at least one memory and thecomputer program code being configured to, with the at least oneprocessor, to cause the apparatus to: select a preferred operating modefor use by the wireless device, the selection being made from at least afull duplex operating mode in which the wireless device can transmit andreceive simultaneously on the same frequency band and a non full duplexoperating mode; and determine to transmit a signal indicating theselected preferred operating mode to a network entity.

In a second exemplary embodiment of the invention there is an apparatusfor a network entity operating in a wireless communications network, theapparatus including: at least one processor; and at least one memoryincluding computer program code, the at least one memory and thecomputer program code being configured to, with the at least oneprocessor, to cause the apparatus to: receive from each of one or morewireless devices operating in the network an indication of a preferredoperating mode for use by the wireless device and selected by thatwireless device from at least a full duplex operating mode in which thewireless device can transmit and receive simultaneously on the samefrequency band and a non full duplex operating mode; and determine foreach of the one or more wireless devices whether or not to support itsindicated preferred operating mode.

In a third exemplary embodiment of the invention there is a method ofoperating a wireless device in a wireless communication network, themethod including: selecting, by the wireless device, a preferredoperating mode for use by the wireless device, the selection being madefrom at least a full duplex operating mode in which the wireless devicecan transmit and receive simultaneously on the same frequency band and anon full duplex operating mode; and determining to transmit a signalindicating the selected preferred operating mode to a network entity.

In a fourth exemplary embodiment of the invention there is a method ofoperating a network entity in a wireless communications network, themethod including: receiving from each of one or more wireless devicesoperating in the network an indication of a preferred operating mode foruse by the wireless device and selected by that wireless device from atleast a full duplex operating mode in which the wireless device cantransmit and receive simultaneously on the same frequency band and a nonfull duplex operating mode; and determining for each of the one or morewireless devices whether or not to support its indicated preferredoperating mode.

In a fifth exemplary embodiment of the invention there is anon-transitory computer-readable storage medium including a set ofcomputer-readable instructions stored thereon, which, when executed by aprocessing system, cause the processing system to carry out the methodof the third exemplary embodiment of the invention.

In a sixth exemplary embodiment of the invention there is anon-transitory computer-readable storage medium including a set ofcomputer-readable instructions stored thereon, which when executed by aprocessing system, cause the processing system to carry out the methodof the fourth exemplary embodiment of the invention.

In a seventh exemplary embodiment of the invention there is a networkapparatus in a wireless communication system, the apparatus including:at least one processor; and at least one memory including computerprogram code, the at least one memory and the computer program codebeing configured to, with the at least one processor, to cause theapparatus to: determine to send, at least one first user equipmentserved by a base station, a message indicating that the at least onefirst user equipment is to operate in a half duplex mode, in which modesome time periods are reserved for the first user equipment to transmitin a frequency band without receiving in the frequency band and othertime periods are reserved for the first user equipment to receive in thefrequency band without transmitting in the frequency band; determine tosend, at least one second user equipment, served concurrently by thebase station with the at least one first user equipment, a messageindicating that the at least one second user equipment is to operate ina full duplex mode in which mode the at least one second user equipmentcan simultaneously transmit and receive in the frequency band; andschedule transmissions to and from the at least one first user equipmentand to and from the at least one second user equipment.

Further features and advantages of the invention will become apparentfrom the following description of preferred embodiments of theinvention, given by way of example only, which is made with reference tothe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a communications network;

FIG. 2 illustrates steps that may be performed in a user device in thecommunications network;

FIG. 3 illustrates steps that may be performed in a user device in thecommunications network;

FIG. 4 illustrates steps that may be performed in a user device in thecommunications network;

FIG. 5 illustrates downlink and uplink sub frame scheduling for firstand second user devices;

FIG. 6 is a schematic illustration of a wireless user equipment; and

FIG. 7 is a schematic illustration of a network entity.

DETAILED DESCRIPTION

Exemplary embodiments are concerned with methods and apparatus foroperating wireless devices in a wireless communications network. Certainembodiments are particularly suitable for use in mobile wirelessnetworks such as a Universal Terrestrial Radio Network (UTRAN), a LongTerm Evolution (LTE) network, LTE-A network and in Wireless LAN (WLAN)networks.

FIG. 1 schematically illustrates a communication network 1 including abase station or access point 2 for communicating over a radio airinterface with one or more mobile user devices 3 and 4 present in ageographical area served by the base station 2. It will be understoodthat the wireless communication network 1 may include a plurality ofsuch base stations 2, each serving a different one of a plurality ofcontiguous geographical areas, although for simplicity only a singlebase station 2 is shown. The communications network 1 further includes acore network 5 for exchanging control signalling and user data with thebase station 2. In one example, if the network 1 is based on a LTEnetwork, the core network may include a mobile management entity 6 and aserving gateway 7 for exchanging control plane signalling and user planedata respectively with the base station 2, with the serving gateway 7connected to a packet data gateway 8 for connectivity to externalnetworks 9, such as the Internet.

In the communication network 1 transmissions from the base station 2 toa user device 3, 4 are on the downlink (sometimes referred to as theforward link) and transmissions from a user device 3,4 to the basestation 2 are on the uplink (sometimes referred to as the reverse link).In the preferred example of an LTE system, the downlink transmissionscheme is based on Orthogonal Frequency Division Multiplexing (OFDM) andthe uplink transmission scheme is based on Single Carrier FrequencyDivision Multiplexing SC-FDMA) In both schemes data is allocated toindividual user devices 3, 4 in terms of resource blocks (RBs) (aresource block includes 12 consecutive sub-carriers in the frequencydomain and one 0.5 ms slot in the time domain). On the downlink, userdata for a user device 3, 4 is carried on the Physical Downlink SharedChannel (PDSCH) and on the uplink, user data from a user device iscarried on the Physical Uplink Shared Channel (PUSCH). Communicationsbetween the base station 2 and a user device 3, 4 can be selectivelyconducted on either a full duplex basis or a non full duplex basis. Ifthe communications are conducted on a full duplex basis, transmissionson the downlink and the uplink can occur simultaneously in the samefrequency band (e.g. at the same carrier frequencies). If thecommunications are conducted on a non full duplex basis, transmissionson the downlink and the uplink are separated in the time domain (i.e.they occur in different time slots) or in the frequency domain (e.g.they occur in different non overlapping bands at different carrierfrequencies).

In the preferred example, based around a modified LTE Time DivisionDuplex (TDD) system, for a user device operating in a cell inconventional non full duplex operation (i.e. half duplex operation), asis normal, for that user device, some sub-frames in each radio frame areallocatable by the network exclusively for uplink transmissions andother sub-frames in each radio frame are allocatable exclusively fordownlink transmissions, whereas for a user device operating in the cellin the new full duplex operation, for that user device, at least somesub-frames in each radio frame are allocatable by the network forsimultaneous uplink and downlink transmissions.

To this end, the base station 2 and the user device 3, 4 are eachprovided with means for implementing full duplex wirelesscommunications. Such means may implement any of the non-linearcancellation techniques disclosed in references [2 to 6] mentionedabove, techniques based upon the linear processing of antenna arrays asdiscussed in reference [1] mentioned above, or indeed any suitabletechnique for achieving full duplex wireless communications.

Furthermore, the base station 2 and the user devices 3, 4 may be each beprovided with multiple antenna arrays and associated signal processingmeans for implementing Multiple Input Multiple Output (MIMO)communications between the base station 2 and a user device 3, 4, on thedownlink or on the uplink, either conventionally in conjunction with nonfull duplex operation, or in conjunction with full duplex operation.Different MIMO modes may be selectively employed, including spatialmultiplexing, transmit diversity, and beam forming.

Accordingly, as is illustrated in FIG. 2, in exemplary embodiments ofthe invention, at periodic intervals, in step 100, each user device 3, 4that is capable of full duplex wireless communications selects apreferred operating mode from at least a full duplex operating mode inwhich the device can transmit and receive simultaneously on the samefrequency band and a non full duplex operating mode. In step 101, eachuser device transmits a signal indicating the selected preferredoperating mode to a network entity, for example base station 2. Eachuser device 3, 4 may also select a preferred transmission rankindicating a preferred number of data layers or streams for transmissionto the wireless device from another device, for example the base station2, and transmit a signal indicating the selected preferred transmissionrank to the network entity. The selection of the preferred operatingmode and/or the preferred transmission rank may at least partly be madeusing measurements of signals received from the another device.

The selected preferred transmission rank and preferred operating modemay be indicated together in the same signal. For example, the signalmay include a field including a first number of one or more bits thatindicate the selected preferred transmission rank and a second number ofone or bits that indicate the selected preferred operating mode.

This information, together with other information, is then used by thebase station 2 when determining what transmission rank to schedule forthat user device 3, 4 and whether to schedule full duplex operation ornon full duplex operation for that user device 3, 4. The base station 2may or may not follow the suggestions supplied by the user device 3, 4.

Referring now to FIG. 3, in a preferred example based on a modified LTETDD system, each full duplex enabled user device 3, 4 determines at step200 whether the amount of data in its uplink buffer (i.e. the amount ofdata currently awaiting to be transmitted on the uplink) is greater thana pre-determined buffer threshold value or not. If no, there is notenough data in the uplink buffer for the user device 3, 4 to requirefull duplex operation and so the user device 3, 4 disregards the optionof selecting full duplex operation as the preferred operating mode andinstead selects, step 201, half duplex operation as the preferredoperating mode and a transmission rank that is estimated to maximisedownlink throughput as the preferred transmission rank.

If yes, step 202, the user device 3, 4 selects as its preferredcombination of operating mode (i.e. full duplex or half duplex) anddownlink transmission rank as the combination estimated to maximisedownlink throughput. At step 203, the user device 3, 4 transmits anindication of the selected preferred transmission rank, the selectedpreferred operation mode and one or more Channel Quality indicators(CQI) to the base station 2. The CQI indicates a modulation scheme andcoding rate in an LTE system and a modulation scheme and transport blocksize in a WCDMA system.

FIG. 4, illustrates individual steps that are performed in step 202 ofFIG. 2. The combination of transmission rank and operation modeestimated to providing the maximum throughput may be determined based onmeasurements of the downlink Signal to Interference Plus Noise Ratio(SINR), at the relevant user device 3, 4, for each available downlinktransmission rank for full duplex operation and for half duplexoperation.

Accordingly, at step 301, for each downlink transmission rank availablefor full duplex operation, the user device 3, 4 determines the downlinkSINR_fd_ib for each i:th MIMO stream and b:th resource block associatedwith that rank in accordance Equation 1 below, and for each downlinktransmission rank available for half duplex operation, the user device3,4 determines the downlink SINR_hd_ib for each i:th MIMO) stream andb:th resource block associated with that rank in accordance Equation 2below:

SINR_(—) fd _(—) ib=S _(—) ib/(I _(—) ib+IULDL _(—) ib)  (Equation 1)

SINR_(—) hd _(—) ib=S _(—) ib/I _(—) ib  (Equation 2)

Where

-   -   S_ib is the desired signal power in the downlink for MIMO stream        i and resource block b after receiver processing at the user        device;    -   I_ib is sum of cell interference (both inter and intra) and        thermal noise power at the user for MIMO stream i and resource        block b; and    -   IULDL_ib is the interference power at the user device's        receiver, for MIMO stream i and resource block b, caused by the        user device's transmitter.

It will be appreciated that for rank 1 transmissions there is just asingle stream, for rank 2 transmissions two spatially multiplexedstreams, for rank 3 transmissions three spatially multiplexed streamsand so on.

The user device 3, 4 may obtain measurements of both S_ib and I_ib inconventional fashion from the Cell Specific Reference Signal (CRS)transmitted on the downlink in LTE systems and used for channelestimation, or alternatively, in conventional fashion from the ChannelState Information RS (CSI-RS) signal transmitted on the downlink inLTE—Advanced systems. The user device 3, 4 may obtain measurements ofIULDL_ib from the Sounding Reference Signal (SRS) transmitted on theuplink in LTE systems and used to measure uplink channel quality. Tothis end, the user device 3, 4 receives at its own receiver the SRStransmitted on the uplink from its own transmitter, and measures theIULDL_ib from this received SRS. In instances of full duplex operationwhere the degree of cancellation of the interference of the uplink onthe downlink is high the IULDL_ib will be correspondingly low and wherethe degree of cancellation of the interference of the uplink on thedownlink is low the IULDL_ib will be correspondingly high.

Table 1 below illustrates for transmission ranks 1 to N (column 1), thecorresponding sets of SINR measurements obtained for full duplexoperation (column 2) and the sets of SINR measurements obtained for halfduplex operation (column 3). Naturally, each set includes a number ofmeasurements that depends upon the rank (i.e. number of streams) forthat set and the number of resource blocks for each stream, although forsimplicity, the number of measurements in each set is illustrated on aper stream basis only (i.e. one measurement per stream)

TABLE 1 Full Duplex SINR Half Duplex SINR Rank Measurements Measurements1 (one stream) SINR_fd_1₁ SINR_hd_1₁ 2 (2 spatially SINR_fd_2₁SINR_hd_2₁ multiplexed streams) SINR_fd_2₂ SINR_hd_2₂ . . . . . . . . .N (N spatially SINR_fd_N₁ SINR_hd_N₁ multiplexed streams) SINR_fd_N₂SINR_hd_N₂ . . . . . . SINR_fd_N_(N) SINR_hd_N_(N)

At step 302, for each set of SINR measurements, the user terminal 3, 4maps the SINR measurements to either one or two CQI index values. Table2 below illustrates the results of this mapping for the full duplex.

SINR measurements and Table 3 below for the half duplex SINRmeasurements

TABLE 2 Full Duplex SINR Rank Measurements CQI 1 (one stream) SINR_fd_1₁CQI_fd_1_(codeword1) 2 (2 spatially multiplexed SINR_fd_2₁CQI_fd_2_(codeword1) streams) SINR_fd_2₂ CQI_fd_2_(codeword2) . . . . .. . . . N (N Spatially multiplexed SINR_fd_N₁ CQI_fd_N_(codeword1)streams) SINR_fd_N₂ CQI_fd_N_(codeword2) . . . SINR_fd_N_(N)

TABLE 3 Half Duplex SINR Rank Measurements CQI 1 (one stream) SINR_hd_1₁CQI_hd_1_(codeword1) 2 (2 spatially SINR_hd_2₁ CQI_hd_2_(codeword1)multiplexed streams) SINR_hd_2₂ CQI_hd_2_(codeword2) . . . . . . . . . N(N Spatially SINR_hd_N₁ CQI_hd_N_(codeword1) multiplexed streams)SINR_hd_N₂ CQI_hd_N_(codeword2) . . . SINR_hd_N_(N)

In the example of an LTE system, for rank 1, assuming so called‘wideband CQI reporting’ (a CQI result based on the complete systembandwidth) the mapping generates one CQI index value because (as thereis no spatial multiplexing with rank 1), the base station 2 wouldgenerate at most a single codeword (as is well known a code word is atransport block which has been processed by the physical layer in termsof CRC addition, channel coding and rate matching) within a transmissiontime interval (TTI) for a user device 3, 4 and so one CQI index value isrequired for that codeword. For ranks 2 and higher, again assuming socalled ‘wideband CQI reporting’, the mapping generates two CQI indexvalues because, in the case of spatial multiplexing, the base station 2would generate two code words within a TTI for a user device 3, 4 and soa CQI per codeword is required. Alternatively, a user device may makeuse of so called ‘sub-band CQI’ reporting where a series of CQI resultsis generated where each result is based upon an assumption that acodeword would span a configured sub-band.

The current LTE specification defines 16 possible CQI index values, eachindicating a different combination of modulation scheme and coding rate.The CQI Table is reproduced below as Table 4.

TABLE 4 CQI index Modulation Code rate × 1024 efficiency 0 out of range1 QPSK 78 0.1523 2 QPSK 120 0.2344 3 QPSK 193 0.3770 4 QPSK 308 0.6016 5QPSK 449 0.8770 6 QPSK 602 1.1758 7 16QAM 378 1.4766 8 16QAM 490 1.91419 16QAM 616 2.4063 10 64QAM 466 2.7305 11 64QAM 567 3.3223 12 64QAM 6663.9023 13 64QAM 772 4.5234 14 64QAM 873 5.1152 15 64QAM 948 5.5547

In this example, in line with current LTE requirements, the mappingresults in each CQI index value being the highest value taken from Table4 that would satisfy the condition that PDSCH transmissions werereceived with a codeword error rate of no more than 10%.

In the preferred example of a modified LTE system, as a CQI report isconfigured to a certain bandwidth (e.g. wide band CQI or sub band CQIover B resource blocks), the SINR to CQI mapping described above, can beunderstood as a two step process including the steps of: (a),calculating an average spectral efficiency over the defined set ofresource blocks and over the streams associated with a codeword and then(b) mapping the spectral efficiency to a CQI index value by (i)comparing the computed spectral efficiency with each of the spectralefficiencies given in Table 4 to determine a difference vector for eachCQI index and (ii) selecting the CQI index which has the smallest valuedifference vector.

One suitable technique for mapping between the measured SINR values andspectral efficiency is described in Mogensen, P.; Wei Na; Kovacs, I. Z,;Frederiksen, F.; Pokhariyal, A.; Pedersen, K. L; Kolding. T.; Hugl, K.;Kuusela, M.; “LTE Capacity Compared to the Shannon Bound”, VehicularTechnology Conference, 2007. VTC2007-Spring. IEEE 65th, Page(s):1234-1238, which teaches that an estimate of the spectral efficiency in([bits/s/Hz]) for the x-th, x=1, 2, codeword can be computed as

$\frac{1}{N_{x}}{\theta \cdot \varepsilon}{\sum\limits_{i \in N_{x}}{\sum\limits_{b \in B_{i}}{\log_{2}\left( {1 + \frac{\gamma_{i,b}}{\beta}} \right)}}}$

where, i is the index for transmitted streams; the operator ∥ indicatesthe cardinality of a set; N_(x) is the set of streams belonging to thex-th codeword with size |N_(x)|; B_(i) is the set of resource blocksbelonging to the i-th stream with the size of |B_(i)| (the cardinalityof |B_(i)| is defined by the number of resource blocks associated withthe CQI computation), ε defines bandwidth efficiency (this depends onsystem parameters, such as the length of the cyclic prefix (CP),), γ_(i,b) is the SINR for the i-th stream and b-th resource block, θ is acorrection factor which is nominally set to one; and β is animplementation dependent constant, dependent for example upon, receivertype.

At step 303, for each available rank for Full Duplex operation, the userdevice 3, 4 generates, based on that rank's CQI index value or valuesand a configuration of the bandwidth (i.e. the number or resourceblocks) that the base station has configured for this CQI report, anestimated total transport block size, T_fd_r, for full duplex operationat that rank assuming transmissions using the modulation and codingscheme (or two schemes for ranks >1) indicated by the CQI index value orvalues. It will be appreciated that for rank 1, the estimated totaltransport block size is an estimate of the size of the single transportblock that can be transmitted, whereas for ranks greater than 1, theestimated total transport block size is the sum of the estimated sizesof the two transport blocks that can be transmitted. Also at step 303,the user device 3, 4 repeats this process for each available rank forhalf Duplex operation to generate an estimated total transport blocksize, T_hd_r; for half duplex operation.

Tables 5 and 6 below illustrate the full duplex T_fd_r and half duplexT_hd_r respectively.

TABLE 5 Full Duplex Total Transport Block Size Rank Full Duplex CQI(T_fd_r) 1 (one stream) CQI_fd_1_(codeword1) T_fd_1 2 (2 spatiallyCQI_fd_2_(codeword1) T_fd_2 multiplexed streams) CQI_fd_2_(codeword2) .. . . . . . . . N (N spatially CQI_fd_N_(codeword1) T_fd_N multiplexedstreams) CQI_fd_N_(codeword2)

TABLE 6 Half Duplex Total Transport Block Size Rank Half Duplex CQI(T_hd_r) 1 (one stream) CQI_hd_1_(codeword1) T_hd_1 2 (2 spatiallyCQI_hd_2_(codeword1) T_hd_2 multiplexed streams) CQI_hd_2_(codeword2) .. . . . . . . . N (N spatially CQI_hd_N_(codeword1) T_hd_N multiplexedstreams) CQI_hd_N_(codeword2)At step 304, the user device 3, 4 selects the full duplex rank havingthe highest value T_fd_r max from the T_fd_r values and the half duplexrank having the highest value T_hd_r max from the T_hd_r values.

At step 305, to select a final preferred operation mode and downlinktransmission rank, the user device 3, 4 takes the ratio of T_fd_r maxand T_hd_r max and compares the ratio to a predetermined thresholdvalue. If the ratio is less than the threshold value, the half duplexoperation mode is selected and the rank of T_hd_r max are selected, butif the ratio is greater than the threshold value full duplex operationand the rank of T_fd_r max are selected. It is anticipated that T_fd_rmax will always be smaller than T_hd_r max because the SINR at thereceiver for full duplex operation will always be smaller than the SINRat the receiver for half duplex operation. Despite, T_fd_r being smallerthan T_hd_r, often the downlink throughput achievable with full duplexoperation will be greater than that achievable with half duplexoperation because, in any given frame, in half duplex operation alimited number of slots are allocated to the downlink whereas in fullduplex operation, in theory, all slots may be allocated for downlink(although in practice this may not be achievable). Accordingly, thethreshold value is set so as to balance the larger transport block sizesexpected for half duplex transmission against the greater number ofslots expected to be available for full duplex downlink transmission todetermine which mode will provide the likely greater downlinkthroughput. The threshold is therefore set at a value for which halfduplex is expected to provide the greater throughput if the ratio isless than it and full duplex is expected to provide the greaterthroughput if the ratio is greater than it.

In an alternative embodiment, at step 305, the sum of T_fd_r max and theprevious scheduled uplink transport block size is compared with T_hd_rmax. If the sum exceeds the T_hd_r max the full duplex mode is selectedand if not the half duplex mode is selected.

Step 201 of FIG. 3 may be performed in a corresponding manner to that ofstep 202, but the process involving only the available combinations ofhalf duplex mode and transmission rank and excluding any considerationof the available combinations of full duplex mode and transmission rank.

In operation, a user device 3, 4 sends reports indicating its currentpreferred RI, preferred operation mode (i.e. half duplex or full duplex)and CQI index value or values on the uplink to the base station 2. Therate at which reports are sent may be periodic, for example at a rateset in a RRC Connection Reconfiguration message or aperiodic, forexample, in response to requests from the base station 2. For example,in current LTE system according to 3GPP TS36.213 v.10.4.0 section 7.2.2:the rank indicator (RI) reporting is an integer multiple MRI [1, . . . ,32] of period NPD [1, . . . , 160] in sub-frames for a TDD system. Theperiodic reports may be transferred using the Physical Uplink ControlChannel (PUCCH) and aperiodic reports using the Physical Uplink SharedChannel (PUSCH).

In current LTE specifications, a Rank Indicator report includes a fieldcontaining a number of bits, the set value of which indicates the userdevice's preferred RI. For example, a field including 3 bits could beused to indicate any selected one of up to 8 transmission rank values.In a preferred embodiment of the present invention, the Rank Indicatorreport includes a field including a first number of bits the value ofwhich is used to indicate the user device's preferred transmission rankfor the downlink and an additional bit the selected value of which isused to indicate whether the user device 3, 4 prefers full duplex modeor non full duplex mode.

In this example, the preferred RI and operation mode are reported at thesame time and hence at the same rate. This is advantageous because itkeeps reporting overheads to a minimum and is acceptable becausechanging channel conditions will likely dictate that transmission rankand operation mode should be changed at similar rates.

In this example a user device 3, 4 reports an RI, an indication ofwhether full duplex or non full duplex operation is preferred and CQIindex value or values. A user device 3, 4 does not report back to thebase station 2 any Pre-coder Matrix indication (PMI) indicating asuggested set of ‘pre-coding weights’ from a pre-defined code book of‘pre-coding weights’ to be applied at the base station 2 for thedownlink transmission and nor does the base station need to indicate toa user device 3, 4 which set of ‘pre-coding weights’ from thepre-defined code book of is to be applied at the base station 2 for thedownlink transmission. Instead, this example, relies on so called ‘noncodebook-based pre-coding’, as is used in transmission mode 9 defined inLTE release 10. In such non codebook-based pre-coding, the layers to betransmitted by the base station 2 to a user device 3, 4 includedemodulation reference signals (DM-RS) that are introduced into thelayers prior to the pre-coding. The transmission of these pre-codedreference signals allows for demodulation and recovery of thetransmitted layers at the user device without the user device havingexplicit receiver knowledge of the pre-coding applied at the basestation 2.

It will be appreciated however that embodiments of the invention are notlimited to arrangements where the downlink transmission utilises noncodebook-based pre-coding. Embodiments of the invention may also includearrangements where the downlink transmission utilises so called‘codebook-based pre-coding’ like transmission mode 3 defined in LTErelease 10 which supports open loop spatial multiplexing, ortransmission mode 4 defined in LTE release 10 which supports closed loopspatial multiplexing. It will be appreciated that if an embodiment ofthe invention uses closed loop spatial multiplexing, then a user device3, 4 will need to feedback Precoding Matrix Indicator (PMI) reports tothe base station 2, in addition to the RI reports, the full duplexoperation or non full duplex operation reports and the CQI reports. Asis well known, a PMI indicates a suggested set of ‘pre-coding’ weightsthat the base station may apply. Open loop and closed loop spatialmultiplexing are well known techniques and so will not be discussed inany further detail.

Referring again to FIG. 1, the base station 2 also periodicallyevaluates whether it can receive full duplex transmission using asimilar process to that described above for the user devices 3, 4, thatis to say, the base station 2 evaluates the cancellation gain ofsuppressing down link transmission from uplink reception and based onthis measurement determines if it is likely that full duplex receptioncan be made. If it is determined that full duplex reception can be made,full duplex mode may be scheduled for those user devices 3, 4 that haveindicated that this is their preferred operating mode. In response toreceiving the RI and CQI reports from the user devices 3, 4, the basestation 2 determines for each user device 3, 4 whether or not to applyfor that user device the preferred transmission rank and whether or notto apply full duplex operation for those user devices 3, 4 that haveindicated this to be their preferred operating mode. Half duplexoperation will automatically be applied for those user devices 3, 4 thathave indicated this as their preferred operating mode. In general, basestation 2 will allocate the rank to a user device 3, 4 that matches theone indicated as being preferred by that user device and typically onlyin cases where there is a small amount of data in the base station'stransmission buffer for a user device, will a lower rank be allocated bythe base station 2.

The base station 2 may schedule downlink and uplink resources among theuser devices 3, 4 using known algorithms such as the round robinalgorithm (which allocates the same amount of resources to each userdevice) or the proportional fair algorithm (which allocates resources touser devices dependent upon achievable data rates at each time instance)or any other type of scheduling algorithm.

In the example of FIG. 1, the user device 3 is on the edge of the cellserved by the base station 2 and the path loss between it and the basestation 2 is so large that it cannot use full-duplex mode efficiently.Hence a feedback RI and CQI report provided by the user device 3 to thebase station 2 indicates that full-duplex is not the preferred mode ofoperation for the user device 3. The user device 4 is closer to the basestation 2 and, as discussed above, based on an SINR measurement the userdevice 4 determines that its preferred operational mode is full duplexso its RI and CQI report provided to the base station 2 indicates thatfull-duplex is the preferred mode of operation. The base station 2determines for each user device 3, 4 a decision of what mode to support.If the base station 2 determines that user device 3 will not beinterfered by full-duplex operation of the user device 4, it can permituser device 4 to use full-duplex operation. The base station 2 maydetermine whether there is sufficient isolation between the user devices3, 4 for the user device 4 to be permitted to use full duplex operationbased on known techniques. For example, based on the direction and timeof arrivals of the user signals at the base station, by using GlobalPositioning System (GPS) coordinates reported by the user devices or byusing path loss measurements made by user devices of the uplinktransmissions from other user devices reported to the base station 2. Insome circumstances, in particular, for rank 1 downlink channels, use ofthe full duplex operation mode instead of half duplex operation incombination with conventional downlink MIMO rank 1 modes (e.g. transmitdiversity or beam forming) provides an increase in throughput. In apreferred example, applicable to the Physical Downlink Shared Channel(PDSCH) and the Physical Uplink Shared Channel (PUSCH) of an LTE system,use of the full duplex mode for communications between the base station2 and a user device 3, 4 doubles the throughput of the downlink anduplink shared channels in the event of a rank 1 channel.

In current LTE TDD systems, seven different frame configuration formatshave been set, each of which defines which sub frames in a frame areallocated for uplink transmissions and which sub frames in a frame areallocated for downlink transmissions. These conventional frame formatsare listed as formats 0 through to 6 in table 7 below.

TABLE 7 Downlink- to-Uplink Uplink- Switch- downlink point Subframenumber configuration periodicity 0 1 2 3 4 5 6 7 8 9 0 5 ms D S U U U DS U U U 1 5 ms D S U U D D S U U D 2 5 ms D S U D D D S U D D 3 10 ms  DS U U U D D D D D 4 10 ms  D S U U D D D D D D 5 10 ms  D S U D D D D DD D 6 5 ms D S U U U D S U U D 7 — DU DU DU DU DU DU DU DU DU DU

In table 7, ‘D’ indicates that a sub frame is allocated for downlinktransmissions, ‘U’ indicates that a sub frame is allocated for uplinktransmissions and ‘S’ indicates a so called special sub frame in which aswitch between downlink transmission to uplink transmissions occurs.Downlink to uplink switch point periodicity may be 5 ms (for thoseconfigurations where sub frames 1 and 6 are special frames) or 10 ms(for those configurations where just sub frame 1 is a special frame). Incurrent LTE systems, the Uplink-Downlink configuration is set on a cellby cell basis (i.e. all user devices in a cell are set the sameconfiguration) and the configuration can be changed dynamically, to takeaccount of varying load conditions on the uplink and on the downlink.The frame configuration is located in the TDD-Config IE which isbroadcasted in SystemInformationBlockType1 which can be decoded by auser device from the Physical Down ink Shared Channel once every second10 ms radio frame.

In a preferred example of the FIG. 1 network being based on an LTE TTDnetwork, a new frame configuration format, listed as format 7 in table7, is defined for full duplex operation. In the new frame configurationformat each sub frame is for downlink transmission and for uplinktransmission. The base station 2 signals the new frame configurationformat to the user device 4 using user specific signalling, for example,an RRCConnectionReconfiguration message (or an RRDConnectionSetupMessage) may be appended to include the full duplex frame configurationand transmitted from the base station 2 to the user device 4.

It will be appreciated that, in this example, at least two frameconfiguration formats are required, one like format 7 in table 7 foruser devices that the base station 2 is going to schedule for fullduplex operation, and one like any of the half duplex formats in table 7for user devices that are (a) full duplex compatible but for which thebase station 2 is going to schedule half duplex operation and (b) legacyuser devices that are not full duplex compatible. In a preferredembodiment, the available frame configuration formats are those shown intable 7 and the applicable half duplex format for a cell (i.e. that tobe used by the user devices served by the base station 2 that are notscheduled for full duplex operation) broadcast in a conventional manner(i.e. using a TDD-Config IE message as discussed above).

The base station 2 schedules for each TTI, which user devices totransmit data to and which user devices to receive data from, and onwhich set or resource blocks. The resulting scheduling decisions aretransmitted from the base station 2 to the user devices on the PhysicalDownlink Control Channel (PDCCH). User devices that are currentlyconfigured in accordance with the full duplex frame configurationformat, can be scheduled to transmit on the uplink and receive on thedownlink in the same sub frame, transmit on the uplink in a sub framebut not receive on the downlink in that sub frame, or receive on thedownlink in a sub frame but not transmit on the uplink in that subframe. User devices that are configured in accordance with a non fullduplex frame configuration format can be scheduled to transmit on theuplink only on sub frames allocated to the uplink and receive on thedownlink only in sub frames that are allocated for the downlink.

In the example being described with respect to FIG. 1, as the userdevice 3 is on the cell edge and cannot efficiently use full-duplextransmission, it is likely that the base station 2 has the same problem(i.e. the path loss is too high for efficient interference processing inthe base station receiver). Accordingly, the base station 2 usesscheduling to adaptively allocate full duplex mode for user devices in acell that can perform the full duplex reception and allocate half duplexmode for user devices in a cell that cannot perform the full duplexreception.

FIG. 5 schematically illustrates scheduling between user device 3 (UE1in FIG. 5) and user device 4 (UE2 in FIG. 5), when, UE1 cannot supportthe full duplex mode but UE2 can and UE1 and UE2 are sufficiently forapart from each other so that their transmissions don't mutuallyinterfere with each other. FIG. 5 is based on the assumption that theTDD frame configuration allocated to half duplex user devices isconfiguration 2 from Table 7. Sub frames in which either UE1 or UE2receive (Rx) on the downlink from the base station (BS) (or converselythe base station (BS) transmits (Tx) on the downlink to either UE1 orUE2) are labelled (D). Sub frames in which either UE1 or UE2 transmit(Tx) on the uplink to the base station (BS) (or conversely the basestation (BS) receives (Rx) on the uplink from either UE1 or UE2) arelabelled (U). For the sake of simplicity, in the time domain, the first5 ms half of two frames are illustrated and in the frequency domain tworesource blocks (RB1, RB2) are illustrated (although for the sake offurther simplicity each RB is show as being in a 1 ms sub-frame, ratherthan a 0.5 ms slot because in current LTE systems scheduling is made atthe sub frame granularity (i.e. two 0.5 ms RBs are always concatenatedtogether in the time domain).

In the example of FIG. 5, the half duplex UE1 receives a downlinktransmission on downlink RB1 in the first sub-frame of frame 1 and thefull duplex UE 2 transmits an uplink transmission on uplink RB1. This ispossible because (a) UE1 and UE2 are sufficiently separated so that theuplink transmission of the full duplex UE2 is suppressed by path loss atthe receiver of UE1 and so does not interfere with the downlinkreception at UE1 and (b) the base station is capable of full duplexoperation to receive the uplink transmission of UE2 (i.e. processing atthe base station ensures that downlink transmission to UE1 does notinterfere with the uplink reception from UE2). In the third sub frame offrame 1 the half duplex UE1 is scheduled an uplink transmission onuplink RB1, but as UE1 is located at the cell edge so that the basestation is not capable of full duplex operation when communicating withUE2. UE1 is not scheduled to receive on the downlink because thatdownlink transmission would interfere with the uplink reception at thebase station. This example in frame 1 illustrates that it may bepossible to use full duplex processing in the base station to receivefrom a full duplex UE while transmitting to a half duplex UE.

In frame 2, full duplex mode transmission and reception is scheduled forUE2 and no transmission or reception is scheduled for UE1. In each ofthe first three sub frames of frame 2, UE2 receives downlinktransmissions on downlink RB1 and RB2 and transmits uplink transmissionson uplink RB1 and RB2. In the fourth sub frame of frame 1, UE2 receivesdownlink transmissions on downlink RB1 and transmits uplinktransmissions on uplink RB1.

In this example, for simplicity, the frequencies of the sub-carriers ofuplink RB1 and the frequencies of the sub-carriers of downlink RB1 arethe same and likewise for uplink RB2 and downlink RB2. However, itshould be appreciated that this need not be the case, so that, whenoperating in full duplex mode within an LTE channel bandwidth, forexample a 10 MHz bandwidth, a UE may simultaneously, transmit using aset of one or more uplink RBs each of which has the same sub carrierfrequencies as an RB in a set of one or more downlink RBs beingreceived, or it may, simultaneously transmit on a set of one or moreuplink RBs each of which has different sub carrier frequencies to eachof those of a set of one or more downlink RBs that are being receivedor, there may be a partial correspondence in terms of the sub-carrierfrequencies of the uplink RBs being transmitted and the downlink RBsbeing received.

Although in the described embodiment the base station 2 utilisessignalling to configure and schedule either full duplex or half duplextransmissions between itself and a user device 3, 4, it will beappreciated that in alternative embodiments the base station 2 mayutilise such signalling to configure and schedule either full duplex orhalf duplex transmissions between a pair of device to device (D2D) nodepairs, for example, the user device 3, 4.

FIG. 6 shows schematically a user equipment or wireless device, 20 inthis case in the form of a mobile phone/smartphone, suitable for use asuser device 3 or 4 in FIG. 1. The user equipment 20 contains thenecessary radio module 21, processor(s) 22 and memory/memories 23,multiple antennas 24, etc. to enable wireless communication with thenetwork as described above.

FIG. 7 shows schematically a network entity 30 suitable for use as thebase station 2 in FIG. 1. The term “base station” is used in thisspecification to include a “traditional” base station, a Node B, anevolved Node B (eNB), or any other access point to a network, unless thecontext requires otherwise. The network entity 30 includes its own radiomodule 31, processor(s) 32 and memory/memories 33, schedulers 34, andmultiple antennas 35 etc to enable wireless communication with the userdevices 3, 4 as described herein above.

Although at least some aspects of the embodiments described herein withreference to the drawings include computer processes performed inprocessing systems or processors, the invention also extends to computerprograms, particularly computer programs on or in a carrier, adapted forputting the invention into practice. The program may be in the form ofnon-transitory source code, object code, a code intermediate source andobject code such as in partially compiled form, or in any othernon-transitory form suitable for use in the implementation of processesaccording to the invention. The carrier may be any entity or devicecapable of carrying the program. For example, the carrier may include astorage medium, such as a solid-state drive (SSD) or othersemiconductor-based RAM; a ROM, for example a CD ROM or a semiconductorROM; a magnetic recording medium, for example a floppy disk or harddisk; optical memory devices in general; etc.

It will be understood that the processor or processing system orcircuitry referred to herein may in practice be provided by a singlechip or integrated circuit or plural chips or integrated circuits,optionally provided as a chipset, an application-specific integratedcircuit (ASIC), field-programmable gate array (FPGA), etc. The chip orchips may include circuitry (as well as possibly firmware) for embodyingat least one or more of a data processor or processors, a digital signalprocessor or processors, baseband circuitry and radio frequencycircuitry, which are configurable so as to operate in accordance withthe exemplary embodiments. In this regard, the exemplary embodiments maybe implemented at least in part by computer software stored in(non-transitory) memory and executable by the processor, or by hardware,or by a combination of tangibly stored software and hardware (andtangibly stored firmware).

As used in this application, the term ‘circuitry’ refers to all of thefollowing: (a) hardware-only circuit implementations (such asimplementations in only analog and/or digital circuitry) and (b) tocombinations of circuits and software (and/or firmware), such as (asapplicable): (i) to a combination of processor(s) or (ii) to portions ofprocessor(s)/software (including digital signal processor(s)), software,and memory(ies) that work together to cause an apparatus, such as amobile phone or server, to perform various functions) and

(c) to circuits, such as a microprocessor(s) or a portion of amicroprocessor(s), that require software or firmware for operation, evenif the software or firmware is not physically present.

This definition of ‘circuitry’ applies to all uses of this term in thisapplication, including in any claims. As a further example, as used inthis application, the term “circuitry” would also cover animplementation of merely a processor (or multiple processors) or portionof a processor and its (or their) accompanying software and/or firmware.The term “circuitry” would also cover, for example and if applicable tothe particular claim element, a baseband integrated circuit orapplications processor integrated circuit for a mobile phone or asimilar integrated circuit in server, a cellular network device, orother network device.

The above embodiments are to be understood as illustrative examples ofthe invention. Further embodiments of the invention are envisaged. Forexample, although the preferred example is described in the context ofan LTE TDD system this is not essential. In another example, a LTEFrequency Division Duplex (FDD) system can be modified such that insteadof having dedicated uplink and downlink carrier frequencies, the fullduplex transmission can occupy both uplink and downlink carrierfrequencies simultaneously for both uplink and downlink transmission bya single network device in some of the sub-frames.

In yet another example, the frequencies reserved for uplink and downlinkin LIE Frequency Division Duplex (FDD) system can be reallocated for 2TDD systems, one operating on the uplink frequency and one on thedownlink frequency.

It is to be understood that any feature described in relation to any oneembodiment may be used alone, or in combination with other featuresdescribed, and may also be used in combination with one or more featuresof any other of the embodiments, or any combination of any other of theembodiments. Furthermore, equivalents and modifications not describedabove may also be employed without departing from the scope of theinvention, which is defined in the accompanying claims.

What is claimed is:
 1. An apparatus for a wireless device operating in awireless communication network, the apparatus comprising: at least oneprocessor; and at least one memory including computer program code, theat least one memory and the computer program code being configured to,with the at least one processor, to cause the apparatus to: select apreferred operating mode for use by the wireless device, the selectionbeing made from at least a full duplex operating mode in which thewireless device can transmit and receive simultaneously on the samefrequency band and a non full duplex operating mode; and determine totransmit a signal indicating the selected preferred operating mode to anetwork entity.
 2. The apparatus according to claim 1, wherein, the atleast one memory and the computer program code are configured to, withthe at least one processor, to cause the apparatus to: select apreferred transmission rank indicating a preferred number of data layersfor transmissions to the wireless device from another device; anddetermine to transmit a signal indicating the selected preferredtransmission rank to the network entity.
 3. The apparatus according toclaim 2, wherein the at least one memory and the computer program codeare configured to, with the at least one processor, to cause theapparatus to: determine to transmit a signal that indicates the selectedpreferred operating mode and the selected preferred transmission ranktogether to the network entity.
 4. The apparatus according to claim 3,wherein the signal comprises a field comprising a first number of one ormore bits that indicate the selected preferred transmission rank and asecond number of one or more bits that indicate the selected preferredoperating mode.
 5. The apparatus according to claim 1, wherein theselection is at least partly based on an amount of buffered data at thewireless device awaiting transmission.
 6. The apparatus according toclaim 5 wherein the at least one memory and the computer program codeare configured to, with the at least one processor, to cause theapparatus to: compare the amount of buffered data to a first thresholdvalue and if the amount of buffered data is greater than the thresholdselect between a fall duplex operating mode and a half duplex operatingmode, and if the amount of buffered data is less than the thresholdselect a half duplex operating mode.
 7. The apparatus according to claim1 wherein the selection is at least partly based on determining which ofa plurality of available combinations of full duplex or half duplexoperating modes and transmission ranks it is estimated will provide ahighest throughput of data received at the wireless device from anotherdevice, wherein a transmission rank indicates a number of data layersfor transmission to the wireless device from the another device; and theat least one memory and the computer program code are configured to,with the at least one processor, to cause the apparatus to determine totransmit an indication of the selected preferred operating mode and anassociated preferred transmission rank to the network device.
 8. Theapparatus according to claim 7, wherein the at least one memory and thecomputer program code are configured to with the at least one processor,to cause the apparatus: to determine a full duplex mode and transmissionrank combination it is estimated will provide a highest throughput ofdata received, in full duplex rode, at the wireless device from anotherdevice; determine a half duplex mode and transmission rank combinationit is estimated will provide a highest throughput of data received, inhalf duplex mode, at the wireless device from the another device;estimate which of the two combinations will provide the highestthroughput of data; select this combination as a preferred combinationof operating mode and transmission rank.
 9. The apparatus according toclaim 8, wherein the at least one memory and the computer program codeare configured to, with the at least one processor, to cause theapparatus to: determine a full duplex mode and transmission rankcombination it is estimated will provide a highest throughput of datareceived, in full duplex mode, at the wireless device from anotherdevice; determine a half duplex mode and transmission rank combinationit is estimated will provide a highest throughput of data received, inhalf duplex mode, at the wireless device from the another device; anddetermine a ratio of an estimated first data block size transmittable tothe wireless device from the another device in a transmission timeinterval using the full duplex mode and transmission rank combinationand an estimated second data block size transmittable to the wirelessdevice from the another device in the transmission time interval usingthe half duplex mode and transmission rank combination and compare theratio to a threshold value and if the ratio is greater than thethreshold select the full duplex operating mode and transmission rankcombination and if the ratio is less than the threshold select the halfduplex operating mode and transmission rank combination.
 10. Theapparatus according claim 1 wherein the at least one memory and thecomputer program code are configured to, with the at least oneprocessor, to cause the apparatus to: determine a full duplex mode andtransmission rank combination it is estimated will provide a highestthroughput of data received, in full duplex mode, at the wireless devicefrom another device; determine a half duplex mode and transmission rankcombination it is estimated will provide a highest throughput of datareceived, in half duplex mode, at the wireless device from the anotherdevice; and determine a sum of an estimated first data block sizetransmittable to the wireless device in a transmission time intervalfrom the another device using the full duplex mode and transmission rankcombination and a previous scheduled second data block for transmissionfrom the wireless device to the another device, compare the sum with anestimated third data block size transmittable to the wireless device ina transmission time interval from the another device using the halfduplex mode and transmission rank combination and, if the sum exceedsthe estimated third data block size select the full duplex mode andtransmission rank combination and if the sum is less than the estimatedthird data block size select the half duplex mode and transmission rankcombination.
 11. The apparatus according to claim 1 wherein the wirelessdevice transmits a signal indicating at least one Channel QualityIndicator for the selected preferred operating mode to the networkentity.
 12. The apparatus according to claim 11 wherein the at least oneChannel Quality indicator is determined based on an SINR measurement forthe selected preferred operating mode taken at the wireless device. 13.An apparatus for a network entity operating in a wireless communicationsnetwork, the apparatus comprising at least one processor; and at leastone memory including computer program code, the at least one memory andthe computer program code being configured to, with the at least oneprocessor, to cause the apparatus to: receive from each of one or morewireless devices operating in the network an indication of a preferredoperating mode for use by the wireless device and selected by thatwireless device from at least a full duplex operating mode in which thewireless device can transmit and receive simultaneously on the samefrequency band and a non full duplex operating mode; determine for eachof the one or more wireless devices whether or not to support itsindicated preferred operating mode.
 14. The apparatus according to claim13, wherein the at least one memory and the computer program code areconfigured to, with the at least one processor, to cause the apparatusto: receive from each of the one or more wireless devices operating inthe network a signal indicating a transmission rank indicating apreferred number of layers for transmissions to that wireless devicefrom another device in the network, in conjunction with that wirelessdevice using its selected preferred operating mode; and determine foreach of the one or more wireless devices whether or not to support itsindicated preferred transmission rank.
 15. The Apparatus according toclaim 1 wherein the apparatus is configured for use in a LTE, LTE-A orCDMA wireless network.
 16. The Apparatus according to claim 13 whereinthe apparatus is configured for use in a LTE, LTE-A or CDMA wirelessnetwork.
 17. A method of operating a wireless device in a wirelesscommunication network, the method comprising: selecting, by the wirelessdevice, a preferred operating mode for use by the wireless device, theselection being made from at least a full duplex operating mode in whichthe wireless device can transmit and receive simultaneously on the samefrequency band and a non full duplex operating mode; and determining totransmit a signal indicating the selected preferred operating mode to anetwork entity.
 18. The method according to claim 17, furthercomprising: selecting, by the wireless device, a preferred transmissionrank indicating a preferred number of data layers for transmission tothe wireless device from another device; and determining to transmit anindication of the selected preferred transmission rank and preferredoperating mode to the network entity.
 19. A method of operating anetwork entity in a wireless communications network, the methodcomprising: receiving from each of one or more wireless devicesoperating in the network an indication of a preferred operating mode foruse by the wireless device and selected by that wireless device from atleast a full duplex operating mode in which the wireless device cantransmit and receive simultaneously on the same frequency band and a nonfull duplex operating mode; and determining for each of the one or morewireless devices whether or not to support its indicated preferredoperating mode.
 20. The method according to claim 19, the method furthercomprising: receiving from each of the one or more wireless devicesoperating in the network an indication of a transmission rank indicatinga preferred number of data layers for transmissions to that wirelessdevice from another device in the network; and determining for each ofthe one or more wireless devices whether or not to support its indicatedpreferred transmission rank.
 21. A non-transitory computer-readablestorage medium comprising a set of computer-readable instructions storedthereon, which, when executed by a processing system, cause theprocessing system to carry out the method of claim
 17. 22. Anon-transitory computer-readable storage medium comprising a set ofcomputer-readable instructions stored thereon, which, when executed by aprocessing system, cause the processing system to carry out the methodof claim
 19. 23. A network apparatus in a wireless communication system,the apparatus comprising: at least one processor; and at least onememory including computer program code, the at least one memory and thecomputer program code being configured to, with the at least oneprocessor, to cause the apparatus to: determine to send, at least onefirst user equipment served by a base station, a message indicating thatthe at least one first user equipment is to operate in a half duplexmode, in which mode some time periods are reserved for the first userequipment to transmit in a frequency band without receiving in thefrequency band and other time periods are reserved for the first userequipment to receive in the frequency band without transmitting in thefrequency band; determine to send, at least one second user equipment,served concurrently by the base station with the at least one first userequipment, a message indicating that the at least one second userequipment is to operate in a full duplex mode in which mode the at leastone second user equipment can simultaneously transmit and receive in thefrequency band; and schedule transmissions to and from the at least onefirst user equipment and to and from the at least one second userequipment.
 24. The network apparatus according to claim 23, wherein theat least one memory and computer program code, are configured, with theat least one processor, to cause the apparatus to: (a) schedule the atleast one first user equipment to receive a transmission to betransmitted by a transceiver operating in full duplex mode in thefrequency band in a first time period of a radio frame; and (b) schedulethe at least one second user equipment to transmit a transmission to thetransceiver in the first time period in the first frequency band. 25.The network apparatus according to claim 24 wherein the at least onememory and computer program code, are configured, with the at least oneprocessor, to cause the apparatus to: (c) schedule the first userequipment operating in the half duplex mode to transmit a transmissionto the transceiver in the first frequency band in a second time periodof a radio frame without scheduling the second user equipment operatingin a full duplex mode to receive a signal in the second time slot in thefirst frequency band from the transceiver.
 26. The network apparatusaccording to claim 24, wherein the at least one memory and computerprogram code, are configured, with the at least one processor, to causethe apparatus to: estimate prior to (a) and (b) that interference at thefirst user equipment that would be caused by the at least one seconduser equipment transmitting the transmission to the transceiver in thefirst time period in the first frequency band will be low enough for thefirst user equipment to receive the transmission from the transceiver.27. The network apparatus according to claim 26 wherein the estimationis at least partly based upon an estimate of the positions of the firstand second user equipments.
 28. The network apparatus according to claim24 wherein the at least one memory and computer program code, areconfigured, with the at least one processor, to cause the apparatus to,prior to (a) and (b), to receive at the network a report from the firstuser equipment indicating that its preferred operating mode is halfduplex mode and a report from the second user equipment indicating thatits preferred operating mode is full duplex mode.